JP2000184622A - Uninterruptible power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an uninterruptible power supply operate properly in accordance with the condition of input power by setting an output voltage and by letting the power supply have optimum input and output characteristics from the aspects of loss and stable supply of electric power. SOLUTION: Having first and second converters 1, 2, a storage battery 6 and a controlling device 11, this uninterruptible power supply inputs AC power and outputs an AC voltage. The controlling device 11 is set to have three voltage ranges; the first voltage range including a reference voltage of a first lower limit voltage or larger and a first upper limit voltage or smaller, the second voltage range lower than the first lower limit voltage and equal to or larger than a second lower limit voltage, and also higher than the first upper limit voltage and equal to or smaller than the second upper limit voltage, and the third voltage range lower than the second lower limit voltage or higher than the second upper limit voltage. If the input voltage is in the first voltage range, this voltage is directly outputted. If it is in the second one, the second converter 2 compensates the voltage to output the first lower limit voltage or first upper limit voltage. If it is in the third one, the first converter 1 outputs the reference voltage from the storage battery 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an uninterruptible power supply, and more particularly to a technique for supplying stable power to a load.

[0002]

2. Description of the Related Art As a circuit system of an uninterruptible power supply, Technical Report No. 596 of the Institute of Electrical Engineers of Japan, "Trends in Uninterruptible Power Supply Systems (UPS)" (Newly Designed Power Supply System Technical Committee, issued July 1996, No. ISSN 0919-9195) ) 1
There is a triport method on page 3 section 3.3.1. In addition, there is an instantaneous interruption compensation method in the section 3.3.4. Furthermore, these two
IEEE as a circuit system combining various types of systems
TRANSACTIONS ON POWER EL
CTRONICS, VOL. 13, NO. 3, MAY
1998, "A Novel On-Line UPS
with Universal Filterung
Capabilities ”is a combination method of serial-parallel converters. This circuit is shown in FIG. 9. When the power supply 7 is normal, the switch 3 is closed, the switch 12 is opened, the converter 1 performs voltage control, and the storage battery is operated. 6, the converter 2 performs current control to compensate for instantaneous fluctuations in the input voltage, and when the power supply 7 fails, the switch 3 is opened and the converter 1 supplies power to the load 8. If a failure occurs in the device such as the converter 2, the switch 3 is opened and the switch 12 is closed to disconnect the load 8 from the device.

[0003]

In the uninterruptible power supply according to the prior art, the converter 1 supplies power to the load 8 when the power supply 7 fails, and when the instantaneous voltage fluctuates, the total capacity of the apparatus is reduced. The compensation can be made by the converter 2 having a small capacity of about 10 to 20%. However, even when the state of the power supply 7 is stable and does not fluctuate at all, the current flows through the converter 2, which causes a problem such as a loss.

An object of the present invention is to provide an uninterruptible power supply which sets an output voltage to provide optimum input / output characteristics in terms of loss and stable power supply, and performs an appropriate operation according to the state of the input power supply. It is to provide a device.

[0005]

The object of the present invention is to provide a first voltage range that includes a reference voltage and is equal to or higher than a first lower limit voltage and equal to or lower than a first upper limit voltage, and a second voltage range that is lower than the first lower limit voltage and equal to or lower than a second lower limit voltage.
And a second voltage range that is higher than the first upper limit voltage and lower than or equal to the second upper limit voltage, and lower than the second lower limit voltage or higher than the second upper limit voltage. A third voltage range is set. If the input voltage is the first voltage range, the input voltage is directly output. If the input voltage is the second voltage range, the input voltage is converted by the second converter. Compensating and outputting the first lower limit voltage or the first upper limit voltage, and if the input voltage is in a third voltage range, the first converter outputs a reference voltage from the power storage mechanism by the first converter. It is solved by performing the operation. A first voltage range that includes a reference voltage and is equal to or higher than a first lower limit voltage and equal to or lower than a first upper limit voltage; a first voltage range that is lower than the first lower limit voltage and equal to or higher than a second lower limit voltage; Setting a second voltage range higher than the first upper limit voltage and equal to or lower than the second upper limit voltage, and a third voltage range lower than the second lower limit voltage or higher than the second upper limit voltage; Is a first voltage range, the input voltage is compensated by a second converter and a reference voltage is output. If the input voltage is in a second voltage range, the input voltage is compensated by a second converter. By performing a second operation of outputting a reference voltage from the power storage mechanism by the first converter if the input voltage is in the third voltage range. ,
Will be resolved. A first switch that opens and closes the input, a bypass circuit that bypasses the second converter and directly connects the input and the output, a second switch that switches the second converter and the bypass circuit, A first converter is connected in parallel with the input or output, a second converter is connected in series with the output or input, and a power storage mechanism is connected to the first input or output. And the control device inputs the output of the detector to control the first and second converters and the first and second switches, and A first circuit configuration in which the first switch is closed and the second switch is turned on to the bypass circuit side to directly output the input voltage, and a first switch is closed and the second switch is turned on in the second converter side And a second circuit configuration for outputting a combined voltage of the input voltage and the second converter; Forming a third circuit configured to output a voltage of the first converter by opening the first switch.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an uninterruptible power supply according to an embodiment of the present invention. An AC power supply 7 is connected to the input, and a load 8 is connected to the output to supply power. There are a converter 1 and a converter 2 which can convert AC / DC into forward and reverse. The converter 1 is connected in parallel with the output, and the converter 2 is connected in series with the input.
The switch 3 opens and closes an input. The switch 4 switches between the converter 2 and the bypass circuit 5. The DC side of converter 1 and converter 2 is connected to storage battery 6. Detectors 9, 10 respectively
Detects the input voltage Vin and the output voltage Vout and inputs them to the control device 11. The control device 11 controls the converters 1 and 2 and the switches 3 and 4.

Next, in the uninterruptible power supply of FIG.
Will be described. FIG. 2 shows the relationship between the input voltage and the output voltage in the first operation. The control device 11 inputs the detected value of the input power and calculates the effective value Vin. V
If in is VL1 ≦ Vin ≦ VH1, the switch 3 is closed and the switch 4 is turned on to the bypass circuit 5 side. At this time, the uninterruptible power supply performs a commercial power supply operation for directly outputting the input voltage. In commercial power supply operation, converter 2 stops. Converter 1 charges storage battery 6 when the voltage of storage battery 6 is discharged. When the storage battery 6 is in a charged state, the storage device 6 performs a no-load operation without power transfer or stops. Vin is VL2 ≦ Vin <V
If L1 or VH1 <Vin ≦ VH2, the switch 3 is closed and the switch 4 is turned on to the converter 2 side. At this time, the uninterruptible power supply performs a compensation operation of outputting a combined voltage of the input power and the converter 2. At the time of the compensation operation, the effective value Vout of the output voltage is set to VL1, Vin> when Vin <VL1.
At the time of VH1, the output voltage of the converter 2 is controlled so as to be VH1 (the effective value Vout when the compensation operation is not performed is indicated by a broken line in FIG. 2). During compensation operation, converter 1 supplies power to converter 2. If Vin is Vin <VL2 or Vin> VH2, switch 3 is opened and converter 1
Backup operation to output the voltage of In the backup operation, converter 2 stops. Here, VL1 is a lower limit value of the output voltage allowable value, and VH1 is an upper limit value. If the allowable output voltage is ± 10% of the reference voltage Vb, VL1 is 0.9 Vb and VH1 is 1.1 Vb. VL
2, VH2 is a voltage determined by the capacity of the converter 2. Change the capacity of the converter 2 to 10 with respect to the capacity of the
VL2 is 0.8 Vb and VH2 is 1.2 Vb. In the first operation, if the input voltage is within the allowable value, almost no loss occurs. If the converter 1 is stopped when the storage battery 6 is in a charged state, the loss is further reduced. If the fluctuation of the input voltage is equal to or less than the capacity of the converter 2, the voltage compensation is performed by the converter 2 having a capacity smaller than the capacity of the uninterruptible power supply by the compensation operation. Since power is supplied from the converter 1 without supplying power, stable power supply can be performed for a long time.

[0008] Next, in the uninterruptible power supply of FIG.
Will be described. FIG. 3 shows the relationship between the input voltage and the output voltage in the second operation. The control device 11 inputs the detected value of the input power and calculates the effective value Vin. V
If in is VL2 ≦ Vin ≦ VH2, the switch 3 is closed and the switch 4 is turned on to the converter 2 side. At this time, the uninterruptible power supply performs a compensation operation of outputting a combined voltage of the input power and the converter 2. During compensation operation, the effective value V of the output voltage
The output voltage of the converter 2 is controlled so that out becomes the reference voltage Vb. However, due to the capacity of the converter 2, Vin <
When VL1 or Vin> VH1, the output voltage of the converter 2 is controlled so as to output Vout proportional to Vin (the effective value Vout when no compensation operation is performed is indicated by a broken line in FIG. 3). Converter 1 supplies power to converter 2 during compensation operation. Vin is Vin <VL2 or Vin>
If it is VH2, the switch 3 is opened and the backup operation for outputting the voltage of the converter 1 is performed. In the backup operation, converter 2 stops. Here, VL1, VH1 and V
L2 and VH2 are voltages determined by the allowable value of the output voltage and the capacity of the converter 2. If the capacity of the converter 2 is designed to be 10 with respect to the capacity 100 of the uninterruptible power supply, VL1 becomes 0.9V.
b, and VH1 becomes 1.1 Vb. Further, if the allowable output voltage is ± 10% of the reference voltage Vb, VL2 is 0.8 Vb and VH2 is 1.2 Vb. In the second operation, if the fluctuation of the input voltage is equal to or less than the capacity of the converter 2, the output voltage can be made constant by the compensation operation. Even if the fluctuation of the input voltage is larger than the capacity of the converter 2, if the output voltage can be set to an allowable value, the voltage is compensated by the converter 2 having a capacity smaller than the capacity of the uninterruptible power supply by performing the compensation operation. Since the loss can be small, and the power is supplied from the converter 1 without supplying the power from the storage battery 6, stable power supply can be performed for a long time.

Next, FIG. 4 is a block diagram of a control device according to the present invention, and a third operation in which the first operation and the second operation are switched and operated will be described with reference to FIG. The effective value detector 111 calculates the effective value Vin of the input voltage. The comparator 1121 inputs Vin and VH1, and Vin
If ≧ VH1, “1” output; if Vin <VH1, “1” output
The comparator 1122 outputs Vin and VL1.
And if Vin ≦ VL1, “1” output, Vin>
If it is VL1, it outputs "0". The OR circuit 1123 takes the logical sum of the comparators 1121 and 1122, and when Vin deviates from the range of VL1 ≦ Vin ≦ VH1, “1”.
Is output. The reset pulse generator 1124 has a period ta.
Generates a reset pulse. The counter 1125 is 11
The rise or fall of the output pulse 23 is counted, and the count value within the ta time is obtained by the reset pulse of the reset pulse generator 1124. Counter 1
At 125, the frequency of voltage fluctuation is determined from the count value within the ta time, and when the frequency is equal to or more than a predetermined value, the first operation is switched to the second operation. In the third operation, by selecting ta sufficiently long, a low-loss operation (first operation) can be performed in a stable state in which the input voltage does not fluctuate, and VL1
In the case of unstable operation that repeatedly fluctuates in the vicinity of VH1 or VH1, an operation (second operation) that does not frequently switch between the commercial power supply operation and the compensation operation is performed so that a stable output is obtained. It is possible to provide an optimum operation according to the state of the vehicle.

FIG. 6 is another block diagram of the control device according to the present invention. A fourth operation for changing the judgment voltages VL1, VH1 or VL2, VH2 will be described with reference to FIG. The effective value detector 111 detects the effective value Vin of the input voltage.
Is calculated. The comparator 1131 inputs Vin and VH2, and if Vin ≧ VH2, outputs “1” and Vin <V
If it is H2, "0" is output. The comparator 1132 has V
In and VL2 are input. If Vin ≦ VL2, “1” is output, and if Vin> VL2, “0” is output. The reset pulse generator 1133 generates a reset pulse having a period tb. The counter 1134 counts the rise or fall of the output of the comparator 1131 and obtains a count value within the time tb by the reset pulse of the reset pulse generator 1133. The counter 1135 counts the rise or fall of the output of the comparator 1132, and obtains a count value within the time tb by the reset pulse of the reset pulse generator 1133. The counters 1134 and 1135 determine the frequency of voltage fluctuation from the count value within the time tb, and determine the determination voltages VH2 and VL2, respectively.
Are given to the means 1136 and 1137 for changing. VH
The changing means 1136 for changing 2 and the changing means 1137 for changing VL2 change VH2 and VL2 according to the commands of the counters 1134 and 1135, respectively, to extend the range of the compensation operation. If the range of the compensation operation cannot be expanded from the capacity of the converter 2, the output current is limited to reduce the output capacity of the uninterruptible power supply, thereby expanding the voltage output range. For example,
The rating of the device is 1 kW / 100 V, and the capacity of the converter 2 is 10
Assuming that the voltage is 0 W / 10 V, the voltage compensation by the converter 2 is ± 10 V, but the voltage compensation by the converter 2 is expanded to ± 20 V by limiting the output current to 10 A at 10 A. 6 and 7 show the case of the first operation, but VL1 and VH1 are changed in the second operation. 4th
In the operation of, when the input voltage repeatedly fluctuates near VL2 or VH2 or near VL1 or VH1, the range of the compensation operation is widened, the mode is frequently switched to the backup operation, and the storage battery 6 discharges. Prevent it from getting lost.

FIG. 8 is a specific example for controlling the converter 1 and the converter 2 in FIG. This is a full bridge circuit using the semiconductor switching elements 101, 102, 103, 104. Reference numerals 105, 106, 107, and 108 denote reflux diodes, 109 denotes a DC smoothing capacitor, and 6 denotes a storage battery. Reference numeral 1141 denotes a unit that outputs a modulated wave that is a voltage command value, and outputs a modulated wave having an amplitude of 0 to 1. 1142 is a means for outputting a carrier wave. The carrier is a triangular wave having an amplitude of 1 and an arbitrary frequency. The comparator 1143 compares the magnitude of the modulated wave with the carrier. “1” when (modulated wave) ≧ (carrier), “1” when (modulated wave) <(carrier)
0 "is output. 1144 is an inverting circuit.
Reference numeral 4 denotes a drive circuit for the semiconductor switching element, which outputs a drive signal that turns on when the input is "1" and turns off when the input is "0". The drive circuit 13 drives 101 and 104, and the drive circuit 14 drives 102 and 103. Further, the drive circuits 13 and 14 delay the ON timing, and
2 and 103 and 104 have a dead time creation function to prevent them from turning on at the same time.

[0012]

As described above, according to the present invention,
By providing optimal input / output characteristics in terms of loss and stable power supply, if there is no change in input voltage, the input voltage is directly output to perform operation with almost no loss, and if the voltage change is small, , Perform compensating operation, and use a small capacity second
, The voltage is compensated by the converter, so that operation with small loss can be performed. Further, since the operation state of the uninterruptible power supply is switched by monitoring the input voltage, it is possible to perform an optimal operation according to the state of the input power supply. Furthermore, in a power supply state where the operation frequently switches to the backup operation,
Since the operating range of the voltage compensation is widened, it is possible to suppress the discharge of the power storage mechanism and extend the life.

[Brief description of the drawings]

FIG. 1 shows an uninterruptible power supply according to an embodiment of the present invention.

FIG. 2 is a diagram showing input / output characteristics of the uninterruptible power supply according to the first operation of the present invention.

FIG. 3 is a diagram showing input / output characteristics of an uninterruptible power supply according to a second operation of the present invention.

FIG. 4 is a block diagram of a control device according to the present invention.

FIG. 5 is a view for explaining the operation of FIG. 4 (third operation);

FIG. 6 is another block diagram of the control device according to the present invention.

FIG. 7 is a view for explaining the operation of FIG. 6 (fourth operation);

FIG. 8 illustrates a converter and its control.

FIG. 9 is a diagram for explaining a conventional uninterruptible power supply of a series-parallel converter combination type;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 1st converter, 2 ... 2nd converter, 3 ... 1st switch, 4 ... 2nd switch, 5 ... Bypass circuit, 6 ... Storage battery, 7 ... Input power supply, 8 ... Load, 9 DESCRIPTION OF SYMBOLS 10 ... Voltage detector 11 ... Control device, 111 ... Effective value detector, 1121, 1
122 ... comparator, 1123 ... OR circuit, 1124
... Reset pulse generator, 1125 ... Counter, 113
1, 1132 ... Comparator, 1133 ... Reset pulse generator, 1134, 1135 ... Counter, 1136 ...
Changing means for changing VH2, 1137 ... Changing means for changing VL2 12 ... Switch, 13, 14 ... Driver circuit for semiconductor switching element, 1141 ... Means for outputting modulated wave, 114
2 means for outputting a carrier wave, 1143 ... a comparator,
1144 ... inverting circuit

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Reiko Kanoda 3-1-1 Sachimachi, Hitachi-shi, Ibaraki F-term in Hitachi Plant, Hitachi, Ltd. F-term (reference) 5G015 FA08 GA06 HA04 HA15 JA05 JA24 JA34 JA52

Claims (6)

[Claims] 1. An uninterruptible power supply having first and second converters, a power storage mechanism, and a control device, receiving an AC power supply and outputting an AC voltage, wherein the control device includes a reference voltage. A first voltage range that is equal to or higher than the first lower limit voltage and equal to or lower than the first upper limit voltage, and lower than the first lower limit voltage and equal to or higher than the second lower limit voltage, and higher than the first upper limit voltage; A second voltage range that is equal to or lower than a second upper limit voltage and a third voltage range that is lower than the second lower limit voltage or higher than the second upper limit voltage;
If the input voltage is in the second voltage range, the input voltage is compensated for by the second converter and the first lower limit voltage or Performing the first operation of outputting the first upper limit voltage and outputting the reference voltage from the power storage mechanism by the first converter when the input voltage is in the third voltage range. Uninterruptible power supply characterized. 2. An uninterruptible power supply device having first and second converters, a power storage mechanism, and a control device, receiving an AC power supply and outputting an AC voltage, wherein the control device includes a reference voltage. A first voltage range that is equal to or higher than the first lower limit voltage and equal to or lower than the first upper limit voltage, and lower than the first lower limit voltage and equal to or higher than the second lower limit voltage, and higher than the first upper limit voltage; A second voltage range that is equal to or lower than a second upper limit voltage and a third voltage range that is lower than the second lower limit voltage or higher than the second upper limit voltage;
If the input voltage is within the second voltage range, the input voltage is compensated by the second converter to output a reference voltage. If the input voltage is within the second voltage range, the input voltage is input by the second converter. Outputting a voltage proportional to the input voltage by compensating for the voltage, and outputting a reference voltage from the power storage mechanism by the first converter if the input voltage is in the third voltage range. An uninterruptible power supply that performs operation. 3. The method according to claim 1, wherein a change in the input voltage is monitored, and the number of times of the change over the first voltage range and the second voltage range is a specified number within a specified time. If it is smaller, the first operation is executed, and if the number of times of the change is equal to or more than the specified number within the specified time, the operation is switched so as to execute the second operation. Blackout power supply. 4. The method according to claim 1, wherein a change in the input voltage is monitored, and the number of times of change over the second voltage range and the third voltage range is equal to or more than a specified number within a specified time. Then, all or part of the first and second lower limit voltages and the first and second upper limit voltages are changed. 5. The circuit according to claim 1, wherein a first switch for opening and closing an input, a bypass circuit for directly connecting an input and an output by bypassing the second converter, and And a second switch for switching between the two converters and the bypass circuit, and a detector for detecting an input voltage and an output voltage, wherein the first converter is connected in parallel with an input or an output, and The converter is connected in series with an output or an input, the power storage mechanism is connected to the DC side of the first converter and the second converter, and the control device is:
Controlling the first and second converters and the first and second switches by inputting the output of the detector, closing the first switch, and moving the second switch to the bypass circuit side A first circuit configuration that is turned on to directly output the input voltage, and a first switch that is closed and the second switch is turned on to the second converter, and the input voltage and the second
An uninterruptible power supply, wherein a second circuit configuration for outputting a combined voltage of the converters and a third circuit configuration for outputting the voltage of the first converter by opening the first switch are formed. Power supply. 6. The uninterruptible power supply according to claim 5, wherein the voltage of the first converter and the second converter is controlled by PWM control.